At present, a wide variety of IMDs are commercially released or proposed for clinical implantation that include a housing that is implanted subcutaneously and typically include elongated medical electrical leads or drug delivery catheters that extend from the subcutaneous site to other subcutaneous sites or deeper into the body to organs or other implantation sites. Typically, the IMD includes a battery-powered implantable pulse generator (IPG) that is coupled with electrical medical leads, a battery-powered implantable monitor that may or may not be coupled with electrical medical leads, a battery-powered drug pump coupled with a drug delivery catheter, etc. Such IMDs include implantable cardiac pacemakers, cardioverter/defibrillators having pacing capabilities, other electrical stimulators including spinal cord, deep brain, nerve, and muscle stimulators, drug delivery systems, cardiac and other physiologic monitors, cochlear implants, etc. Typically, the battery-powered component of the IMD is implanted subcutaneously at a surgically prepared site, referred to as a “pocket”. The surgical preparation and initial or replacement IMD implantations are conducted in a sterile field, and the IMD components are packaged in sterile containers or sterilized prior to introduction into the sterile field. However, despite these precautions, there always is a risk of introduction of microbes into the pocket. Surgeons therefore typically apply disinfectant or antiseptic agents to the skin at the surgical site prior to surgery (e.g., chlorhexidine, gluconate, povidone-iodine, isopropyl alcohol, ethyl alcohol), directly to the site before the incision is closed (e.g., gentamicin, vancomycin), and prescribe oral antibiotics for the patient to ingest during recovery (e.g., sefuroxin, gentamicin, rifamycin, vancomycin).
Despite these precautions, infections do occur. In addition, once the pocket becomes infected, the infection can migrate along the lead or catheter to the heart, brain, spinal canal or other location in which the lead or catheter is implanted. Such a migrating infection can become intractable and life-threatening, requiring removal of the IMD in the pocket and associated devices, such as leads and catheters. Removal of a chronically implanted lead or catheter can be difficult and dangerous. Aggressive systemic drug treatment is also provided to treat the infection.
There is long history of the actual or proposed use of anti-infective agents coated on IMDs for prevention of infection. For example, use of antibiotics and antiseptics has been described. However, actual use of antibiotics as coatings for permanently implantable medical devices has been limited. One reason logical reason for such limited use is the potential development of strains of bacterial resistant to the antibiotics. Over time, the effective concentration of the antibiotic in the coating will decrease to a level below which development of resistant bacterial strains becomes a concern.